1. Field of the Invention: exposure function for deciding shutter speed and f-stop for determining the amount of exposure based on the results of photometry.
2. Description of the Prior Art:
Cameras are available having an automatic exposure function (so-called "AE cameras") for measuring the illuminance or light value of incident light and deciding an appropriate shutter speed and f-stop based on a program diagram or the like in accordance with the results of photometry. In order for an AE camera to photograph a subject in an appropriate manner, the range of exposures for which settings can be made is predetermined in terms of shutter speed and f-stop (e.g., 1/1000 -1/15 sec. for shutter speed and f2-f16 for f-stop). When the measured light value of incident light is outside the abovementioned range (as when the environment is dark), the AE camera is incapable of setting the proper exposure, in which case the shutter-release button of the camera is locked to prohibit photography.
However, there are times when the operator of an AE camera wishes to perform photography in a region of low illumination, as when photographing a night scene, fireworks or the like. At such times, prohibition of photography in an AE camera in the manner described above is highly inconvenient.
Although AE cameras which permit a locked shutter-release button to be unlocked are available, the shutter speed usable when the button is unlocked is fixed at 1/15 sec. A shutter speed of this value does not allow photography of fireworks or the like.